This proposal is focused on the problem of chemically mediated synaptic transmission processes in the Clarke's column of the spinal cord. The specific aim of the proposed project is to correlate chemical sensitivity of neurones in the Clarke's column (emphasis being on the neurones of the dorsal spinocerebellar tract i.e. DSCT cells) to various potential neurotransmitter agents (acetylcholine, norepinephrine, 5- hydroxytryptamine, histamine, glutamic, aspartic and gamma-aminobutyric acids, glycine, ATP and cyclic AMP) with sensory inputs from peripheral receptors. It is known that strong descending influences modulate afferent information postsynaptically at the level of second-order sensory neurones within the spinal cord. It would be, therefore, of interest to see to what extent activation of descending monoaminergic pathways affects excitability of the DSCT cells to its receptor inputs. The proposed problems will be approached by microelectrophoretic technique in combination with extra-and intracellular recording procedures. If a significant correlation between chemical sensitivity to a certain putative neurotransmitter and sensory inputs in a particular cell population could be established, one should try a more refined and dscriminative approach by using intracellular recording technique in conjunction with extracellulr application of a putative transmitter (with latter technique it is not expected to test more than one substance). The measurements will be made for the changes in membrane potentials, conductance, reversal potentials as well as for determination of ion species participating in the membrane process initated by putative transmitter. As each of these measurements tested with a transmitter candidate is shown to coincide with the process evoked by the physiologically released transmitter, a great degree of certainty is obtained in establishing identity of action between putative and natural transmitter.